Coal liquefaction process using ash as a catalyst

ABSTRACT

A method for the liquefaction of coal using a solvent extraction process in which finely-divided coal, a solvent, and a catalystacting ash derived from coal are admixed and subjected to solvent extraction conditions. The ash utilized in the solvent extraction process is a substantially carbon-free residue resulting from the decarbonization of coal.

United States Patent Gatsis 51 June 20, 1972 54] COAL LIQUEFACTIONPROCESS 3,488,279 1 1970 Schulman ..208/l0 USING ASH AS A CATALYST3,503,863 3/1970 Gatsis ..208/l0 X 3,503,864 3/1970 Nelson.........208/10 X [72] Inventor: John G. Gatsis, Des Flames, 1]]. 3,505,2024/1970 Nelson.... .....208/10 X 3 505 203 4/1970 Nelson ..208/l0 X Unirsa] l Prod cts C D Y [73] Ass'gnee n; es 3,514,394 5/1970 Wilson eta]... 2023/10 3,575,897 4/1971 Sprow .1208, 10 X [22] Filed: Dec. 18,1970 Primary ExaminerDelbert E. Gantz [2|] 99676 AssistantExaminerP. F.Shaver AttorneyJames R. Hoatson, Jr. and Robert W. Erickson [52] U.S. Cl..208/l0, 208/9 [51] Int. Cl. ..Cl0g 1/06, ClOg 1/08 [57] ABSTRACT [58]Field of Search ..208/ 10, 9 A method for the liquefaction of coal usinga Solvent extrao tion process in which finely-divided coal, a solvent,and a [56] References cued catalyst-acting ash derived from coal areadmixed and sub- UNITED STATES PATENTS jected to solvent extractionconditions. The ash utilized in the solvent extraction process is asubstantially carbon-free 3343339 8/1964 residue resulting from thedecarbonization of coal. 3,488,278 l/l970 3, l 62.594 12/1964 7 Claims,No Drawings BACKGROUND This invention is related to a process for theconversion of 5 carbonaceous materials such as coal to liquid products.More specifically, this invention is related to a process for theconversion of coal to liquid products by solvent extraction of the coalusing a suitable liquid as the solvent and employing a catalyst-actingash which improves the yield of valuable hydrocarbon products fromsolvent extraction processes.

Solid reserves of carbonaceous substances such as coal, lignite, etc.,are abundant relative to petroleum reserves and represent a valuablesource of hydrocarbons to supplement or replace those convenientlyderived from petroleum. As reserves of crude oil continue to be used uprapidly, the need for an economical substitute becomes greater. Theenergy requirements in industrial countries have created a shortage inthe supply of hydrocarbons which could be alleviated by thesupplementation or substitution of solid-fuel-derived hydrocarbons forthose derived from petroleum. Several processes for converting coal tovaluable liquid products are known to those skilled in the art of coalliquefaction. High pressure hydrogenation and solvent extractiontechniques have been developed, the latter of which is related to theprocess of the present invention. In the processes of solvent extractionknown to prior art, finely-divided coal or other particulatecarbonaceous material is placed in contact with a solvent at solventextraction conditions, usually in the presence of hydrogen gas, and theliquified part of the solid is subsequently separated from the remainingsolid material by filtration. centrifugation or a similar operation. Theliquified material is generally separated from the solvent and isfurther processed by conventional means such as hydrocracking ordistillation. while the solvent is conventionally recycled to theextraction process. In some solvent extraction processes which have beendeveloped. the solid residue in the effluent from solvent extraction isalso subjected to further processing in order to recover all possiblevaluable hydrocarbon products therefrom. Such treatments of the residualsolids include for example. destructive distillation and coking.

Schemes for the use of catalysts to promote the liquefaction andhydrogenation of coal in solvent extraction processes have beendisclosed in prior art. Various conventional hydrogenation catalystssuch as palladium or homogenous catalysts such as compounds of tin,nickel, molybdenum, tungsten, or cobalt have been proposed for theseprocesses. Such catalysts and the schemes for their use suffer from theeconomic and technical difficulty imposed on them by the desirability ofseparating the catalyst from the finely divided solid residue of coalleft by solvent extraction in order that the catalyst may be used morethan once. These catalysts are relatively expensive to create, and theseparation of a catalyst from the particulate residue resulting fromsolvent extraction is difficult and expensive. The elimination of thisseparation step in using a catalyst to aid solvent extraction would thusbe both an economic and technical advancement of processes known toprior art.

Another difficulty encountered in the use of catalysts in solventextraction processes is the rapid decline in effectiveness undergone bycatalysts under the process conditions necessary for solvent extractionand product separation. The swift deterioration in catalyst activity isdue partly to the high content in coal and similar solids of metallicand other substances which poison the catalyst upon exposure thereto.Catalysts in processes known to prior art are deactivated also by theunavoidable presence thereon of coke and are separated from this cokefor reuse only with difficulty and expense. A means for eliminating theabove described difficulty would overcome an important barrier to aneffective and efficient process for solvent extraction utilizing acatalyst material.

SUMMARY OF THE INVENTION Therefore, it is an object of this invention toprovide a method for the liquefaction of solid carbonaceous materialswhereby valuable liquid hydrocarbons are obtained as the product. It isa specific object of this invention to provide an effective andefficient method for the solvent extraction and hydrogenation ofcarbonaceous materials by utilizing a catalyst to aid in liquefactionand to improve the products of the process. In accordance with theseobjectives. this invention provides a method for obtaining valuableliquid hydrocarbons from solid carbonaceous materials which. in ageneral embodiment, comprises: (a) subjecting a solid carbonaceousmaterial in admixture with a suitable solvent and a catal \stacting ash,the latter being an ash resulting from the decarbonization of coal orsimilar carbonaceous material, to solvent extraction conditionsincluding the presence of hydrogen gas: and, (b) separating the liquidhydrocarbon residuum from the resultant mixture.

The above-stated steps constitute those essential to the inventiveprocess, and may be combined with methods for the reuse of hydrogen gas,solvent, or the solid part of the resultant mixture. The inventiveprocess may be used in combination with the same general schemes forsolvent extraction of coal as have been disclosed in prior art. Amongthe benefits to be derived from the inventive process are threeimportant ones. First, the separation of the catalyst from the residualundissolved coal in order to reuse it is no longer required. Second,catalysts may be produced by the process itself. Third, the poisoningand coking which inactivate other catalysts are irrelevant in thisprocess.

The present invention is based on the discovery that the ash producedfrom coal when it is decarbonized possesses catalytic properties. Whencommingled with a carbonaceous solid and a solvent, and subjected tosolvent extraction conditions, this ash produces an increase in thefraction of valuable hydrocarbon liquid products obtainable throughsolvent extraction.

DETAILED DESCRIPTION Although the process of this invention will bedescribed in terms of the utilization of bituminous coal to form liquidhydrocarbonaceous products, it is within the concept of the presentinvention to apply the inventive process to the solvent extraction ofbituminous coal, sub-bituminous coal, lignite, oil shale, tar sand, andother solid carbonaceous materials.

Many solvents have been disclosed for processes of solvent extraction.Some solvents, which tend to give up hydrogen to the carbonaceous solid,including for example, Decalin, Tetralin and Biphenyl, are known ashydrogen donors. Other solvents disclosed, which are often used in thepresence of hydrogen gas under pressure, include napthalene,methylnapthalene, etc. Any of the above mentioned solvents, which arenoted as examples, may be used in the present inventive process as wellas any other solvents which will perform the same function.

Particular embodiments of solvent extraction in the process of thepresent invention will depend upon the particular carbonaceous solid tobe liquified, the particular solvent utilized, and the type ofextraction zone employed. The advantages of particular solvents, and theadvantages of particular solvent extraction conditions to be utilized inthe extraction of particular coals are well known to those skilled inthe art. The typical range of solvent extraction conditions includes atemperature of about F. to about 900 F a pressure of about oneatmosphere to about 300 atmospheres, and the presence of hydrogen gas.The catalyst-acting ash may be added to the mixture of solvent and coal,to the coal, or to the solvent, prior to, or after the coal and solvententer the reaction zone. Typi cally, the solvent and coal are combinedat weight ratios in the range of from about 1 part solvent to 1 partcoal up to about 5 parts solvent to 1 part coal. The amount ofcatalyst-acting ash added to the coal and the solvent should be between2 percent and percent of the weight of the combined coal and solvent.When the mixture of coal, solvent and ash has been subjected to solventextraction conditions for a length of time sufficient to extract themaximum amount of valuable hydrocarbon liquid from the coal, thehydrocarbon residuum to be recovered as the product may be separatedfrom the solid residuum by methods familiar to those skilled in the art.Various procedures are known to those skilled in the art for utilizingthe liquid residuum resulting from subjection of the solvent, coal, andash to solvent extraction conditions. It is usual but not necessary tothe present process to separate the solvent from the hydrocarbonsobtained from the coal in the solvent extraction, and to recycle thesolvent for further use. The coal-derived hydrocarbons may be processedfurther by fractionation, hydrogenation and other means, to increasetheir utility. The means of separating the liquid residuum from thesolid residuum in the mixture resulting from solvent extraction are wellknown. Examples of typical means suitable within an embodiment of thisinvention are centrifugation and filtration.

One method, suitable within the scope of the present process, fordecarbonization of coal or other suitable material to be used as thecatalyst-acting ash in the present inventive process, would be to burncoal in the conventional manner, as fuel and to recover the ash as thedecarbonized product. In another suitable example of decarbonization,coal is subjected to solvent extraction and the solid residuum isemployed as the catalyst-acting ash. In a third method ofdecarbonization, coal which has been solvent extracted is subjected tolow temperature coking or carbonization. The products of coking includea liquid component and a solid component. Coking conditions include atemperature sufficient to drive off a large fraction of the volatilematerial from the charge to the coking zone and the absence, in thecoking zone, of oxygen. In a method of coking preferred for use indecarbonization within the scope of the present process, the temperatureof the coking zone should not exceed about I, 1 50 F. This temperaturewill determine the greatest fraction of volatile material which canpresent inventive process include anthracite coal, bituminous coal,lignite, oil shale, tar sand, or other solid carbonaceous materials fromwhich a suitable solid residuum may be obtained for use as a catalyticash. Decarbonization comprises essentially the separation of thenon-carbonaceous materials in the solid to be decarbonized from asubstantial fraction of the carbon therein.

Decarbonized catalytic ash is the result of the application of a methodof decarbonization to a carbonaceous solid, the means of saiddecarbonization being dependent upon a particular embodiment ofdecarbonization, as exemplified by the above-described methods but notlimited thereto.

In a preferred method of decarbonization in the present inventiveprocess, substantially complete decarbonization of the catalyst-actingash would be effected by subjecting a coal, in turn, to solventextraction, low temperature coking and burning. The energy obtained inburning the residue from a coking operation could be used to maintainthe necessary high temperature in the solvent extraction and cokingoperations. The decarbonization effected by burning in the preferredmethod requires that a temperature below about l,l F. be maintained inthe decarbonization zone and that sufficient oxygen be present thereinto combine with essentially all of the carbon thereon. The solidremainder of a coal which has been subjected to substantially completedecarbonization is preferred for use in the process of the presentinvention. The particular source of the ash used is not essential to ageneral embodiment of the present invention excepting that said ash mustbe derived from some naturally occurring carbonaceous substance such ascoal. Such an ash would normally contain a variety of minerals, therelative proportions of which in the composition of the ash will dependon the particular coal which is to be utilized to form said ash in aparticular embodiment of the present invention. Typical constituents ofcoal ash and the approximate limits of the fraction in which they occurin the ash of coals mined in the United States is shown as follows:

TYPICAL CONSTITUENTS OF U.S. COAL ASH Constituent Usual range of percentSi O 2 30-60 09.0 MgO be driven oi? as a vapor under coking conditions.The liquid effluent from a cracking zone is composed of the volatilematerial driven off under said coking conditions. This liquid componentmay be admixed with a liquid resulting from solvent extraction of acarbonaceous material and processed therewith, or may be furtherprocessed in a number of ways well known to those skilled in the art ofhydrocarbon processing. Some fraction of a liquid product from solventextraction, a liquid product from coking, or both, may be utilized asthe solvent, or a fraction thereof, within the scope of the presentinvention in the present solvent extraction process. The liquidcomponent recovered and the solid component recovered from a coking zOnemay be separated from one another by methods well known to previous art.The solid which results from coking the solid residuum of a solventextracted coal is composed of ash and coke. It has been known that thesolid which results from coking a coal may be burned as fuel. Within thescope of the present inventive process, burning the resultant solid fromcoking would comprise a method of decarbonizing the catalytic ash to beutilized. Decarbonization may comprise solvent extraction of a coal.Decarbonization may also comprise coking a coal or coking the solidresiduum from solvent extracting a coal. Decarhonization may alsocomprise burning a coal in air, burning the solid residuum from solventextracting a coal in air, or burning the solid resulting from coking acoal, or the solid residuum of a solvent extracted coal, in air.Decarbonization may also comprise the partial or complete destructivedistillation of a coal. Materials which may suitably be decarbonized toyield the catalytic ash contemplated within the scope ofthc An ash usedas catalyst-acting ash may be treated, within the scope of the presentinvention, to increase its catalyst activity with water, steam, acids,bases, or other means. The shape and form of the catalyst may be changedafter the ash is decarbonized within a general embodiment of theinventive process. For example, the ash may be crushed, ground, pilled,extruded, filtered etc.

PREFERRED EMBODIMENTS A preferred embodiment of the present inventiveprocess comprises the following procedure. A United States minedbituminous coal with a 20 percent, by weight, content of volatilematerials is pulverized to particles small enough to pass through a 14mesh Tyler screen, or smaller, mixed with Tetralin on a 5:l weight basisof solvent to coal and to this is admixed about 5 percent, by weight, ofcatalyst-acting ash. This mixture of coal, Tetralin and ash iscontinuously passed into an upflow slurry extraction zone under solventextraction conditions, including about 2,000 psig. hydrogen pressure anda temperature of about 850 F., sufficient to liquify about percent ofthe coal entering the process. The effluent residuum from the extractionzone is separated into two components, one of which comprises the solidresiduum in the effluent. The solid residuum in the effluent issubjected to conventional low temperature coking conditions including atemperature below 1,150 F. during which substantially all of thevolatile content of the solid residuum is driven off and recovered. Theresultant coke and ash is burned in a conventional decarbonization zoneto provide heat for the prior steps of the process, and, from thesubstantially carbon-frcc ash, a

part thereof, sufficient to provide 5 percent, by weight, of thesubsequent feed to the solvent extraction process, is retained andutilized therein as described above. The liquid residuum separated fromthe solid residuum in the effluent from the solvent extraction zone isfurther processed by distillation and fractionation, and a solvent isthereby recovered and recycled to provide a continuous supply of solventfor the solvent extraction process.

I claim as my invention:

1. A process for converting a solid carbonaceous material to normallyliquid hydrocarbons which comprises the steps of:

a. solvent extracting said solid material with a hydrocarbonaceoussolvent, at solvent extraction conditions, and in contact with adecarbonized catalytic ash; and

b. separating the resultant mixture into a liquid residuum and a solidresiduum and recovering said liquid residuum as said liquidhydrocarbons.

2. The process of claim 1 further characterized in that said catalyticash is derived from said solid residuum.

3. The process of claim 1 further characterized in that said catalyticash is derived from the decarbonization of said solid

2. The process of claim 1 further characterized in that said catalyticash is derived from said solid residuum.
 3. The process of claim 1further characterized in that said catalytic ash is derived from thedecarbonization of said solid residuum.
 4. The process of claim 1further characterized in that said solvent extraction conditions includea hydrogen atmosphere.
 5. The process of claim 1 further characterizedin that said solid carbonaceous material is coal.
 6. The process ofclaim 1 further characterized in that said solid residuum is subjectedto coking at a temperature below about 1,150* F. to produce saidcatalytic ash.
 7. The process of claim 1 further characterized in thatsaid solid residuum is burned in air at a temperature below about 1,150* F. to produce said catalytic ash.